Basic Research—Technology

Retreatability of a Bioceramic Root Canal Sealing MaterialDarren Hess, DDS,* Eric Solomon, DDS, MA,† Robert Spears, PhD,‡ and Jianing He, DMD, PhD*

Abstract

Introduction: The efficacy of retreatment techniques forBC Sealer (BCS) (Brasseler USA, Savannah, GA) removalhas not yet been assessed. The purpose of this study wasto evaluate the efficacy of solvent and rotary instrumen-tation in the removal of BCS when used in combinationwith gutta-percha (GP) as compared with AH Plus sealer(Dentsply, Tulsa, OK). Methods: The mesiobuccalcanals of 40 mandibular molars were instrumentedand obturated with either GP/AH Plus with warmvertical compaction or GP/BCS using a single cone.The groups were subdivided into samples with themaster GP cone placed to the working length (WL) orintentionally 2 mm short of the WL. Canals were then re-treated using heat, chloroform, rotary instruments, andhand files. The ability to regain the WL and patencywere evaluated as well as the time required to removeobturation material. Representative samples were alsoanalyzed via scanning electron microscopy. Results:The WL was not regained in 70% of samples withBCS/master cone short of the WL. Patency was not re-established in 20% of samples with BCS/master coneto the WL or in 70% of samples with BCS/master coneshort of the WL. Conclusions: Conventional retreat-ment techniques are not able to fully remove BCS. (J En-dod 2011;-:1–3)

Key WordsBioceramics, obturation, retreatment, root canal sealer

From the *Departments of Endodontics, †InstitutionalResearch, and ‡Biomedical Sciences, Baylor College ofDentistry, The Texas A&M University System Health ScienceCenter, Dallas, Texas.

Supported by a research grant from the AAE Foundation.Address requests for reprints to Dr Jianing He, Department

of Endodontics, Baylor College of Dentistry, 3302 Gaston Ave,Dallas, TX 75246. E-mail address: jhe@bcd.tamhsc.edu0099-2399/$ - see front matter

Copyright ª 2011 American Association of Endodontists.doi:10.1016/j.joen.2011.08.016

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Brasseler USA (Savannah, GA) recently introduced a bioceramic sealer in an attemptto provide an obturationmethod that can be successfully and predictably performed

by a majority of practitioners while taking advantage of its biocompatibility and physicalproperties (1). According to the manufacturer, BC Sealer (BCS) is a premixed, inject-able, radiopaque, bioceramic material composed of zirconium oxide, calcium silicates,calcium phosphate monobasic, calcium hydroxide, and filler and thickening agents.BCS is hydrophilic and uses moisture in dentinal tubules to initiate and complete itssetting reaction. The working time can be more than 4 hours at room temperature.The setting time is dependent on the presence of moisture in dentinal tubules andmay range from 4 hours to more than 10 hours in very dry canals. The web site statesthe sealer has no shrinkage upon setting, resulting in a gap-free interface between gutta-percha (GP), sealer, and dentin. It also states the sealer is highly biocompatible and isantibacterial during the setting reaction because of its highly alkaline pH (2, 3).

The properties of an ideal obturation material or sealer were outlined by Gross-man (4). Several of these properties have thus far been shown by bioceramic sealers inlimited published research. The apical sealing ability of a bioceramic sealer (iRoot SP;VerioDent, Vancouver, BC, Canada) with GP in a single-cone technique was recentlyshown to be as effective as iRoot SP or AH Plus (Dentsply, Tulsa, OK) with GP in thecontinuous wave condensation technique (5). Zhang et al (3) also showed the antimi-crobial activity of iRoot SP for Enterococcus faecalis. An additional property of an idealmaterial as yet not addressed in studies of bioceramic sealers is the ability to be easilyremoved from canals if necessary. Because calcium silicate phosphate-based biocer-amic materials are known to be hard upon setting, the ability to retreat canals obturatedwith BCS is a current concern for practitioners (6). The purpose of this study was toevaluate the efficacy of conventional solvent and rotary instrumentation in the retreat-ment of GP and BCS as compared with AH Plus.

Materials and MethodsSample Preparation

Mesiobuccal roots of 40 extracted human mandibular first molars were sectionedfrom teeth using a diamond disk and stored in 0.5% NaOCl. Only canals of less than20� curvature and mature apices were included. Patency was confirmed by extendinga #10 Flexofile (DentsplyMaillefer, Tulsa, OK) 1mmpast the anatomical apex. Theworkinglength (WL) of each canal was established with a #10 Flexofile 1 mm short of where the filetip exits onto the root surface. The canal was instrumented using a crown-down techniquewith EndoSequence 0.04 tapered nickel-titanium rotary instruments (Brasseler) at 500revolutions perminute (rpm) tomaster apical file size 35. Threemilliliters of 5.25% NaOClwas used as the irrigant. The smear layer was removed by irrigating with 2 mL 17% EDTAfollowed by 2 mL 5.25% NaOCl and a final rinse of 2 mL of sterile saline. A 30-G Max-i-Probe irrigating needle (Dentsply) was used for all irrigation. The canals were driedwith paper points. Patency was reconfirmed before obturation with a #10 Flexofile.

The teeth were randomly divided into two groups of 20 to be obturated with GP/AHPlus or GP/BCS. These groups were further subdivided into two groups of 10. In group1, BCS was used, and a single GP master cone was placed to the full WL. In group 2, BCSwas used with a single GP cone, but themaster GP cone was trimmed to fit approximately2 mm short of the WL. Group 3 was obturated using AH Plus sealer and the continuouswave compaction technique with a GP master cone and backfilled with GP using theObtura II (Obtura Spartan, Fenton, MO). Group 4 was obturated with AH Plus sealerand CWC as in group 3, but the master cone was fitted short of the WL as in group2. EndoSequence (Brasseler USA, Savannah, GA) 0.04 tapered GP points were used

Retreatability of BC Sealer 1

TABLE 1. The Ability to Regain the WL, Patency, and Time Required for Retreatment in Different Groups

Group 1 (%) Group 2 (%) Group 3 (%) Group 4 (%)

WL regained 100a 30b 100a 100a

Patency regained 80a,c 30b 100c 100c

Time required (min) 7.14 � 2.27a 5.48 � 1.58a,b 3.73 � 1.09b 5.28 � 2.32a,b

Different letters indicate statistically significant difference. For the WL regained, group 2 is significantly different from groups 1, 3, and 4 (P = .000); for patency regained, a significant difference is found between

groups 1 and 2 (P = .035), 2 and 3 (P = .0015), and 2 and 4 (P = .0015); and for the time required, group 1 is significantly different from group 3 (P = .003).

Basic Research—Technology

in all groups. For the AH Plus groups, the sealer was introduced into thecanal via a paper point to length. Then, the master cone was coated withAH Plus sealer and placed to the appropriate length. For the BCS groups,the sealer and single-cone technique were used according to manufac-turer recommendations. The intracanal tip was inserted into thecoronal third of the canal. Two calibration markings of BCS weredispensed into the canal. A #15 Flexofile was then used to coat the canalwalls with BCS to the WL. The master GP cone was then coated with BCSand slowly inserted into the canal to the appropriate length. Each canalorifice was sealed with Fuji IX GP glass ionomer restorative material (GCAmerica Inc, Alsip, IL). All specimens were stored at 37�C in 100%humidity for 2 weeks.

RetreatmentAll groups were retreated with the same technique. An activated

System B 0.06-tapered plugger (SybronEndo, Orange, CA) was intro-duced at 200�C to resistance and withdrawn to remove coronal obtu-ration material. Three to four drops of chloroform were thenintroduced into the reservoir. EndoSequence 0.04 tapered NiTi rotaryinstruments were then introduced into the canal system at 600 rpmin a crown-down technique. Rotary instruments were advanced 2 to3 mm into the canal system followed by flute clearing. This was repeateduntil the WL was reached or resistance was met. If the WL was reached,crown-down instrumentation was performed using EndoSequence 0.04rotary instruments (to size 40) at 500 rpm to the WL to remove the re-maining obturation material. If the WL was not reached, small hand files(C-Files, C+ Files, and Flexofiles sizes 6, 8, and 10, Dentsply) were usedin an attempt to penetrate or bypass blockages. When WL was reached,the canal was instrumented to length with EndoSequence 0.04 rotaryinstruments as described above. If WL was not reached, the canalwas instrumented with EndoSequence 0.04 rotary instruments to themaximum length reached.

Five ml of 5.25% NaOCl was used as the irrigant in each canal. Theend-point of instrumentation during the retreatment phase was deter-mined when a size 40 EndoSequence 0.04 rotary instrument reached

Figure 1. Residual BCS in the canal space (original magnification 50�). (A) A sam2 showing BCS in the apical canal space.

2 Hess et al.

the WL or was otherwise found unable to advance further apically.The ability to reach the WL and regain patency was determined foreach canal. The time required to retreat each canal was also recorded.All sample preparation, treatment, and evaluation were performed bya single operator.

Scanning Electron MicroscopyThe roots were scored longitudinally using a ½ round carbide bur

and wedged apart. Representative specimens were fixed with 10%formalin solution for 24 hours and then dehydrated with ascendingconcentrations of ethanol (30%–100%) and air dried. Each specimenwas sputter-coated with gold and examined with a scanning electronmicroscope at 15 kV. The apical area and foramen were examined at50� magnification.

Statistical AnalysisThe time required for material removal per group was measured

in minutes and expressed as mean � standard deviation. Groupcomparisons were performed using one-way analysis of variance anda Student-Newman Keuls post hoc test. Pearson chi-square analysesand Fisher exact tests were performed using SPSS 16.0 (SPSS Inc,Chicago, IL) to analyze the ability to reach the WL and regain patency.A P value of # .05 was used to determine significance.

ResultsThe Ability to Regain the WL and Patency

The WL was re-established in 100% of samples in groups 1, 3, and4 and in 30% of group 2 (Table 1). Chi-square tests indicated this differ-ence was significant (Pearson chi-square value = 18.781, P = .000).

In groups 3 and 4, patency was re-established in 100% of samples.Patency was regained in 80% of group 1 and 30% of group 2 (Table 1).The Fisher exact test indicated significant differences between groups 1and 2 (P = .035), 2 and 3 (P = .0015), and 2 and 4 (P = .0015). Nosignificant difference was noted between groups 1 and 3 or 4.

ple from group 1 showing BCS in the apical foramen. (B) A sample from group

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Basic Research—Technology

Time Required for Obturation Material RemovalThe average times required for retreating each group are summa-

rized in Table 1. Group 1 took the longest time to retreat followed bygroups 2, 4, and 3. One-way analysis of variance indicated a significantdifference between groups (F = 5.461, P = .003). Post hoc tests noteda significant difference between groups 1 and 3. No significant differ-ence was noted between groups 2 and 4.

Electron MicroscopyScanning electron microscopic micrographs of representative

samples revealed debris and material remaining in all groups. In group1, the apical foramen appeared filled with BCS (Fig. 1A). In the samplesfrom group 2, residual BCS was noted in the apical canal space andforamina (Fig. 1B).

DiscussionThis study evaluated the retreatability of BCS. The results indicate

obturation with BCS, and a single GPmaster conemay result in blockageof the apical foramen and a loss of patency in some cases. The WL wasre-established in 100%of samples with themaster cone seated to theWLregardless of the sealer or obturation technique. However, patency wasonly regained in 80% of BCS samples with the master cone to the WL.This may be explained by the results of scanning electron microscopicanalysis, which showed what appeared to be BCS remaining in the apicalforamen and preventing the re-establishment of patency in thesesamples.

With the master cone intentionally seated short of the WL, BCSproved to be impenetrable in 70% of samples for the WL and patency.It must be noted that this group represents improper usage of BCS butwhat may occasionally occur clinically. WL and patency were, however,re-established in 30% of this group. This may be explained by the abilityof small hand files to navigate through voids within BCS or bypass thesealer in an irregularly shaped canal. Files are unlikely to penetrateBCS because of the hardness upon setting of bioceramics, but insome cases unset sealer may be penetrable. The inability to regainthe WL and/or patency may compromise retreatment by preventingproper cleaning and shaping of the apical canal space, which mayharbor bacteria.

The average time required for removing obturation material wasalso significantly longer in group 1 versus group 3. The average differedby 3.4 minutes and may be attributed to additional time and effortrequired to regain patency in several BCS samples. The lack of signifi-cant difference between groups 2 and 4 may be attributed to less time

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devoted to group 2 when samples were early on confirmed to be apicallynonnegotiable.

It was previously noted that ‘‘the key is using bioceramics asa sealer, not a filler’’ (1, 7). It was also suggested that retreatment beaccomplished with ultrasonics in the coronal third to half, followedby chloroform, rotary instruments, and hand files for the remainderof canal space (1, 7). This technique proved ineffective in somesamples in the present study and indicates the need for a newtechnique or solvent to be developed. Similarly, a previous studyshowed both nickel-titanium rotary instrumentation and ultrasonicswere ineffective in completely removing MTA obturations (8). However,ultrasonic instrumentation was previously shown to be effective in hardpaste removal and may be suggested in some cases of BCS retreatment(9, 10). In conclusion, the results of this in vitro study suggest thatconventional retreatment techniques are not always able to fullyremove BC Sealer.

AcknowledgmentsThe authors thank Brasseler for supplying materials used in

this study.The authors deny any conflicts of interest related to this study.

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Pract 2009;2:13–7.2. Available at: www.brasselerusa.com/pdf/B_3160_ES%20BC%20Sealer%20NPR.pdf.

Accessed September 1, 2010.3. Zhang H, Shen Y, Ruse ND, Haapasalo M. Antibacterial activity of endodontic sealers

by modified direct contact test against Enterococcus faecalis. J Endod 2009;35:1051–5.

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ability. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;107:e79–82.6. Kossev D, Stefanov V. Ceramics-based sealers as new alternative to currently used

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10. Krell KB, Neo J. The use of ultrasonic endodontic instrumentation in theretreatment of a paste-filled endodontic tooth. Oral Surg Oral Med Oral Pathol1985;60:100–2.

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